Management Detail

Mites, Yellow Spider

Reason for Concern:1) Major raspberry pest species in British Columbia and Whatcom County, WA.
2) Sporadic problem in southwest Washington.
3) Yellow and two-spotted mites are the 2 most prevalent species of plant-feeding spider mites inhabiting raspberry foliage. Both species feed on chlorophyll on the underside of leaves.
4)Feeding reduces plant vigor, may cause premature leaf drop, contribute to potential for winter injury and yield loss.

Identification/Symptoms:
Yellow mites are about 2/3 the size of two-spotted mites and much paler. Populations tend to increase earlier in the season than two-spotted mites. Leaves that have been injured by feeding exhibit lower rates of photosynthesis, increased transpiration, deformed leaves, and lower chlorophyll content. This injury causes mottled leaves that may become brown or bronze.

Life Cycle:
Yellow spider mites overwinter as females within protected micro-habitats in raspberry fields. Females emerge in the spring or early summer, disperse and begin to colonize the plants, moving upward on canes as the season advances, laying eggs on the leaves. Eggs hatch into larvae in 4 to 6 days. A complete life cycle requires 1 to 3weeks. Populations usually increase through June and July, with potential for rapid increase after harvest in August. In fall, adults cease feeding and populations decline as a result of natural predators. Females migrate from raspberry plants to overwintering sites. There are several overlapping generations each year.

This mite has become a major pest species of raspberries in British Columbia and Whatcom County. They have also been a sporadic problem in southwest Washington.

Sample minimum of 4 sites, 40 leaflets total. Adjust frequency of sampling dependent on weather, population dynamics, population life cycle, and predator population.

They are about two-thirds the size of twospotted mites and much paler in color. This can lead to underestimates of their populations especially early in the season when twospotted spider mite numbers are still quite low.

They also tend to build up earlier in the season than Twospotted mites.

Their feeding reduces plant vigor and causes leaves to be mottled, turn brown, and drop prematurely.